1. Field of The Invention
This invention relates generally to methods for utilizing the energy present in foundry blast furnace gases and, more particularly, to a process for utilizing the latent heat of gases developed within a cupola furnace or other shaft furnaces having correspondingly high gas temperatures.
2. Description of The Prior Art
The energy expenditure in ore reduction is considerable; the blast furnace itself uses about 66% of the total energy of a metallurgical plant for the production of crude iron. Approximately 3000 Nm.sup.3 of air are required for the burning of one ton of coke. Efforts to conserve heat energy during such a process have been principally directed toward decreasing amounts necessary for processing using coke gas, natural gas, blast furnace gas, heating oil, etc. Another purpose sought to be accomplished by such conservation methods is the utilization of the heat of exhaust gases of metallurgical processes to support the production of high temperatures for the extraction of metal. More specifically, in the production of crude iron and steel it is possible and highly desirable to increase the economy of the metallurgical process by using higher input temperatures of the processing gases.
It is also known that a portion of the heat present in blast furnace gas may be recovered using heat pipe recuperators. Heat recovered in this manner is typically used to provide hot air or hot water to a disintegrator or a venturi washer, respectively. Thereafter, the blast furnace gas is wet-cleaned to eliminate the pyrophoric properties of the dust particles contained therein.
Alternatively, the blast furnace gas may instead be burned as raw gas in a combustion chamber during generation of the hot blast used to operate the furnace. As the dust particles are no longer pyrophoric following combustion, only dry-cleaning of the blast furnace gas is required. In accordance with such prior art techniques, any blast furnace gas which is not needed for hot blast generation is released into the atmosphere via the chimney, thereby wasting the heat energy contained therein.
Techniques for making more efficient use of the heat present in the waste blast furnace gas have been proposed. For example, it has been proposed to utilize the blast furnace gas not needed for hot blast generation to generate electrical current in a steam power station connected downstream.
For a more detailed description of this technique, reference may be had, for example, to an article by E. Freuntsh and A. Rudolph entitled "Concept for a Modern Hot Blast Cupola Furnace Installation", Zeitschrift Gesseri 76, 1989, No. 10/11. There are, however, several disadvantages associated with this technique. Because of the relatively small size of most foundry cupola furnaces, the generating capacity of the associated turbine is limited to 1.5 to 3.0 MW, at best. As such, the initial investment required to purchase and install the necessary generating equipment may be prohibitively expensive, or the period required to recover such an investment may be unacceptably long. Moreover, less modern plants often have insufficient space to accommodate the elaborate equipment needed to generate electricity from steam.
It is therefore an object of the present invention to provide a process for efficiently utilizing the latent heat of shaft furnace gas, thereby substantially reducing the amount of heat released into the atmosphere.
It is a further object of the present invention to provide a process which is space-efficient as well as economical to install and operate.